A common therapeutic approach to setting and realigning extremity bone fractures is to implant an intramedullary implant, i.e. a nail for re-establishing or restoring the original position of the extremity bone fragments. Such fractures are generally fractures of the femur or the tibia. A main problem when dealing with the re-establishment of the position of the extremity bone fragments is to find the correct rotary orientation of the extremity bone fragments to avoid substantial damages of the hip or the knee owing to a mal-position of the extremity bone fragments.
A common approach for dealing with the orientation problem is to freehand estimate the correct rotary orientation of the extremity bone fragments with respect to each other. This however leads to substantial deviations of the rotary orientation of the fragments, so that substantial damages of the hip or the knee may occur.
Another approach is to permanently monitor the entire rotary and positional orientation of the extremity bone fragments and the intramedullary nail. This however leads to a high X-ray load and further does not allow for exact positioning of the bone fragments, as the geometry of the anatomy does not allow for exact spatial impression of the position and orientation of the bone fragments.
A femoral neck anteversion guide is for example known from U.S. Pat. No. 5,728,128, according to which a femoral neck anteversion guide is provided for use with a femur having a prepared intramedullary channel, wherein the guide includes a radiolucent stem having a distal end for inserting into the prepared intramedullary channel, and a radio opaque angle locator wire embedded within the stem at a known angle for allowing the femoral neck angle and femoral neck anteversion to be determined. This however also leads to a high X-ray load and further may lead to a non-exact positioning of the extremity bone fragments with respect to their orientation in relation to each other.